Caluclate total of null, empty string, undefined in an array Javascript

Question

I have an array like this below

const userArray = ['school', 'science', '', '', null, 'bachelors', 'final', undefined, null]

As you can notice, i have 2 empty string, 2 null and 1 undefined in it. So the total is 5.

how can i loop through each time and still get total count of empty string, null and undefined in the array.

phi-rakib · Accepted Answer · 2020-10-24 02:00:40Z

3

You can use Array filter.

const userArray = [
  "school",
  "science",
  "",
  "",
  null,
  "bachelors",
  "final",
  undefined,
  null,
];
let ret = userArray.filter((x) => !x).length;
console.log(ret);

edited Oct 24, 2020 at 2:00

answered Oct 24, 2020 at 1:30

phi-rakib

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6 Comments

Ravi K Over a year ago

can you also specify please how did u find out null "" and undefined. How does !Boolean(x)) || [] help for this

phi-rakib Over a year ago

when casting null, undefined and empty string to boolean its always returns false and I used empty array if there is no boolean false item it will return zero.

Sebastian Simon Over a year ago

@RaviK || [] isn’t part of that expression, and !Boolean(x) is equivalent to !x. See the documentation about falsy values.

phi-rakib Over a year ago

@user4642212 you are right. Do not need use empty array because if no elements pass the test array filter method returns an empty array.

phi-rakib Over a year ago

@Ravi K you are right. I just used it to make it readable. Check the code now.

|

theonly1me · Accepted Answer · 2020-10-24 01:43:06Z

1

You can use the Array.prototype.filter() method in order to remove the non falsy values from the array and calculate the length of the filtered array like below:

const userArray = ["school", "science", "", "", null, "bachelors", "final", undefined, null];
  
const filteredArray = userArray.filter(value => !value);
console.log(filteredArray.length);

edited Oct 24, 2020 at 1:43

answered Oct 24, 2020 at 1:38

theonly1me

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